Apparatus for underground retorting



Dec. 10, 1963 RF. K RUEGER APPARATUS FOR UNDERGROUND RETORTING 2 Sheets-Sheet l Filed July 20, 1959 INVENTOR. @OLA/'VD AT K/EUEGE/Q Eifer 2 Dec. 10, 1963 R. F. KRUEGER APPARATUS FOR UNDERGROUND RETORTING' 2 sheets-snaai 2 Filed July 20, 1959 .FIG-,5

23? (ffm ATTORNEY UnitedStates Patent O 3,113,623 APPARATUS FOR UNDERGR RETORTING Roland F. Krueger, Placentia, Calif., assignor to Union @il Company of California, Los Angeles, Calif., a corporation of California Filed July 20, 1959, Ser. No. 828,106 3 Claims. (Cl. 166-59) This invention relates to a novel method and apparatus for uniformly heating an elongated region of mineral deposits located beneath the earths surface, and more particularly concerns a method Iand apparatus for the thermal recovery of hydhocarbon values from subterranean deposits comprising the same.

A number of processes have been proposed whereby heat is employed to facilitate the recovery of hydrocarbon values from subterranean deposits such as bituminous sands, oil shale, bituminous and sub-bituminous coals, oil-soaked diatomite, heavy petroleum deposits, etc. ln most of said processes at least part of the heat is supplied from a burner positioned in a bore hole drilled into the deposit. For example, according to one process which has been `applied to the treatment of tar sand deposits, a plurality of relatively closely-spaced holes is drilled into the deposit, and heat is generated in a selected number of these holes by combustion of gas or other fuel in la suitably positioned burner device. The surrounding sand is thereby heated and the volatile petroleum fractions are driven towards a production bore hole from which they are recovered. .'Ilhe heavier ends which fail to vol-atilize are pyrolyzed by continued heating. As previously practiced, a single burner has been positioned at the base of the formation or at a point along the combustion tube. This technique results in localized heating, which is useful with shallow formations but not readily `applicable where the formation is vertically extended. Attempts to use this localized heating to transmit heat to an elongated zone within subterranean deposits have employed ow reversal methods, alone, or with packed annular zones of coarse inert material around the burner zone, or with `an annular fluidized bed of iinely divided inert solids. In the flow reversal method of heating, a combustion tube is concentrically placed Within the bore hole and extended nearly to the base of the hole. Combustible gases and air are mixed in the tube and ignited at a selected point. The flame front is prevented from rising to the top of the burner by flame arrestors positioned Within the burner upstream from the llame. The combustion gases pass down the extended burner tube to the base of the hole Where they reverse their direction and ilow upwardly through the annulus between the burner Itube and bore casing. lI-t has been found that `a high temperature zone within the shale deposit exists immediately adjacent the burner flame, and that the temperature of the shale at points vertically removed from this high 'temperature zone are substantially less. This type of operation is not entirely satisfactory because the heat is not eicicntly distributed and because the localized thigh temperature zone causes thermal failure of the burner tube. While use of a lfluidized bed of solids within the annulus between the burner and casing improves heat transfer to the shale, it does not completely eliminate the uneven heating along the bore hole and is disadvantageous in that it causes a high erosion rate of the metal surf-aces.

lt is a purpose of `this invention to provide an improved method for subterranean heating. It is also a purpose of the invention to provide a unique burner construction which achieves uniform heating over an extended length and has a long service life.

These purposes are achieved by providing a continuous elongated combustion zone extending the length of an ice elongated portion of the mineral deposits. The elongated combustion zone is achieved by use of a porous metallic, glass or ceramic combustion tube and Will be described by reference to the drawings which form a part of this application.

In the drawings, FIGURES l, 2 5 and 6 shovw the placement of the novel burner construction in the mineral deposits. FIGURES 3 and 4 show alternative features of construction of `the burner tubes. Although FIGURES 1, Zand 5 show a vertical disposition of the burner tubes, it is apparent -that a horizontal or inclined placement could also be employed, if desired.

Referring norw to FIGURE l, a mineral deposit, B, is shown located beneath an upper layer, A, which may comprise gravel, earth or stone or `an unheated portion of the mineral deposit. In accordance with this invention, a hole is bored through the 'earths surtiace and into the mineral deposit. A metal casing 1 is positioned Within `the bore hole in the conventional manner. Disposed within casing 1 are concentric tubes 2 and 3. Casing l, land tubes Z and 3 are closed at their upper ends. Conduit 4 connects with casing 1 to provide for removal of flue gases, conduit '5 communicates Iwith tube 2 for the introduction of `air or gas, and conduit 6 cornmunicates with inner tube =3, also for the entrance of air or gas. The unique construction of this invention is in the use of a gas-permeable tube 7 connected to the lower portion of central tube 3. Permeable tube 7 is sealed at its lower end by plate `fi which may be permeable, but is preferably impermeable to gas llow. Any suitable connection between permeable tube 7 and metal tube 3 may be employed, such as by cementing, threading or by use of a collar joint.

In operation, natural gas or other gaseous fuel is introduced Athrough conduit 6 into central tube 3. rllhe gas flows down into tube 7 `and passes through the Walls thereof into a flowing air stream which is introduced into tube 2 through conduit 5. The llow of gas through tube 7 into the air stream is lachieved by maintaining a higher pressure on the gas stream than on the air stream. Combustion is initiated in a conventional manner in the annular zone between tubes 2 and 7, and takes place along the entire length of tube 7, thereby providing an elongated combustion zone which may be of any suitable length corresponding to the ylength chosen for the permeable tube -7. y'Ille flue gases are discharged from the lower open end of tube 2 and reverse their direction of flow to pass upwardly through the annular zone between casing l and tube 2, and are removed through conduit yt. Heat is transmitted from the combustion zone by radiation to this upwardly flowing stre-am of flue gases and to lthe mineral deposits in zone B throughout the entire length of the burning zone, and heat is transmitted by convection from the flue gases to the mineral deposits. By this method a combustion zone with -a uniform temperature is maintained along the length of the mineral deposit. Although casing yl is shown to extend the length of the bore hole, it may be considerably shorter where the mineral matrix is suiciently consolidated so as not to tall into the hole. Suitable consolidation may occur naturally or be achieved by coking the hydrocarbons in the deposit immediately adjacent the bore hole.y This coking may be 'accomplished by introducing high temperature combustion gases into the hole.

Conventional ignition techniques presently employed to ignite gas burners in oil Wells lean be employed in the annulus surrounding fthe burner to ignite the burners of my invention. These techniques themselves constitute no inventive step in my system; they merely serve for the ignition `of the gas stream after it passes through the porous Wall and enters the annular combustion zone surrounding the porous burner. Among the suitable ignition techniques which are employed in the annular zone surrounding the porous burners are the following:

Dynamite and percussion caps;

Electrically actuated -heating coils and spark plugs which are positioned within the annular combustion zone and which are initiated by a supply of electrical energy from above ground; and

Chemical ignition techniques wherein a capsule of sodium or potassium is dropped into the well bore and followed by injection of water. The sodium or potassium is then released by mechanical breaking or dissolution of the capsule to react with Water and release heat to ignite the gas.

Referring now to FIGURE 2, a modified form of the invention is shown. In this embodiment, a single tube 16 is concentrically disposed within casing 9. The gas and air are introduced into tube 1h via inlets 11 and 12, respectively, and the gas-air mixture flows downwardly through tube into permeable tube 13 which is shown to be connected to the lower end of -tube 10 by a collar joint. The gas and air stream diuses through tube 13 into [the combustion zone which surrounds the same. The gas is ignited by any of the aforedescribed techniques and the resultant combustion occurs on the outside of this ltube and is prevented from backing into the permeable tube 13 by proper adjustment of the gas and air flow rates. lIf desired, central tube 1G may be extended downwardly as indicated so as to insure that the gases from the combustion zone flow to the base of the formation before reversal into an upwardly directed ilow to the flue gas outlet conduit 14.

FIGURE 3 shows an alternative method of construction for the gas permeable tube, and can be used to obtain a burner of greater strength than is possible with glass or ceramic tubes, alone. This construction comprises a central metal tube 15 which is perforated at suitable intervals by holes 16 and is sealed at its lower end by cap 20. A sleeve 17, constructed of a permeable ceramic or sintered glass material, surrounds lthe perforated portion of tube 15. The diameters of tube 15 and gas-permeable sleeve 17 are so chosen to insure a tight iit. The permeable sleeve extends a substantial distance, D, above the perforated portion of tube 15 to prevent gas llow from bypassing the permeable sleeve and flowing between the sleeve rand the tube. A Suitable sealing material 18 is placed above and below the permeable sleeve 17 to insure a gas-tight't, and is suitably held in place by coupling 19. If desired, the perforated portion of tube 15 can be on a separate piece of pipe and thereby permit connection to any suitable length of pipe to position fthe burning zone at any depth in the mineral deposit. Also if desired, several of these burning zones may be provided on a single string of vpipe separated by an impermeable portion of pipe, thereby permitting simultaneous `heating of multiple zones of mineral deposits. The thickness, W, of permeable sleeve 17 is selected to maintain suflicient thermal insulation between the `outer burning zone and metal tube 15. This is to eliminate any difficulties encountered due to the differences in thermal expansion of the dissimilar ceramic sleeve and the tube.

FIGURE 4 shows another embodiment of the permeable tube burner. This construction comprises a central tube 21 which is perforated similarly to tube 15 of FIGURE 3, and is similarly closed` at its lower end. Surrounding the perforated portion of tube 21 is a second concentric rtube 22 which is supported by rings 23. Tube 22 Ais also provided with a plurality of perforations. Between tubes 22 and 21 is packed an annular bed of unconsolidated silica, sand or quartz grains, which is permeable to gas ow. These grains fare prevented from falling through 4the perforations in tubes 21 and 22 by outer screen 24 and inner screen 25. Again, these burning zones may be constructed on separate pieces of pipe and connected to any desired length of pipe to permit the proper location within the mineral deposit.

FIGURE 5 illustrates an alternative type of construction. The gas permeable burner 26 in this embodiment is constructed of a gas permeable metal and is connected to a supply of air and `combustible gas. The gas and air ow into this permeable burner and diffuse into the annular lzone between the burner and the casing wall. The gas is ignited by any of the -aforedescribed techniques and the resultant combustion occurs in this annular zone along the entire length of the permeable lburner 26. A second concentric tube 27 may surround the permeable burner to insure that the combustion gases will flow to the base of the formation before reversal to the point of removal above the ground. Use of a permeable metal tube simplies construction and provides a burner which is somewhat easier to install than a glass or ceramic burner.

Another embodiment of the invention is illustrated by FIGURE 6. In this embodiment, a single tube 28 is concentrically positioned within casing 29. A ceramic rod 30, which is of a length corresponding to the depth of the mineral deposit, is supported within inner tube 28. lInlet 32 for the introduction of a combustible gas mixture, and outlet 3l for the removal of ue gas, communicate with tube 28 and casing 29, respectively. Gas and air ilow downwardly (through tube 28 and are Withdrawn through conduit 31. Combustion is initiated by igniting the gas stream flowing out of tube 31. However, any other conventional ignition technique is suitable. This combustion is permitted to back up into the burner until the flame front exists at the lower end of tube 28. The ceramic rod 30 is lowered so that its lower end is within the combustion zone at the base of tube 28. The ceramic rod slowly heats up by conduction, and a red-hot zone progresses up the length of rod 30. As this zone moves up the ceramic rod, the combustion zone follows it until a combustion zone exists within tube 2S along the entire length of the 4ceramic rod. An annular ring 33 may be placed within tube 2S above the ceramic rod to momentarily increase the combustible gas flow rate and thereby prevent the combustion zone from moving up tube 28 to the gas inlets or, if desired, tube 28 may be of a reduced diameter at its upper end to serve the same purpose. Other llame arrestors, such as screens or grids, may also be employed. The ceramic rod 30 is shown to be movable in a vertical direction. However, to simplify construction, particularly where the depth of the mineral formation is known, the ceramic rod may be rigidly supported within tube 28.

Suitable ceramic material for constructing the aforementioned gas-permeable elements may comprise permeable ceramics of alumina, zirconia, sandstone, and aluminum silicates such as sillimanite, or clays. These gas-permeable ceramics are commercially available in a wide rang of permeabilities and in a variety of shapes, including tubular elements.

Gas-permeable glass suitable for use in this invention is made by sintering of glass powders to obtain a shatterproof porous glass permeable to gas flow. This type of glass is also commercially available.

Suitable gas-permeable vmetals for construction of the burners of this invention are made by sintering of metal powders. able in bronze and a wide range of stainless steel alloys, such as 304, 309, 316, 347, nickel, Monel, etc. The permeabilities of these metals may range from a value of cubic feet of air per minute per square foot at 0.01 psi. pressure drop for a one-sixteenth inch thick stock of a highly permeable material to a permeability of 27 cubic feet of air per minute at l0 psi. pressure drop for a oneeighth inch stock of low permeability material.

A typical `example of this Yinvention is as follows: The apparatus shown by FIGURE 5 is employed to supply heat to a tar sand deposit 50 feet below the earths surface. The deposit is 30 feet rthick, and it is desired to supply 31,00() B.t.u.s per hour to the sand. A two and one-half inch bore is drilled -into the deposit and a gaspermeable stainless steel burner made from one-eighth These sintered metals are commercially avail- A one-fourth inch pipe is connected to the top of the metal burner tto supply 310 cubic feet per hour of a combined gas and air stream. In order to insure even diffusion of the combustible mixture into the annulus surrounding the burner, it is necessary to maintain a high pressure drop through the burner walls relative to the gas fiow pressure drop down the porous metal tube. A stainless steel of relatively low permeability is chosen to provide a diffusion pressure drop which is l() to 830 times as great as the gas flow pressure drop within the permeable metal burner. The actual diffusion pressure drop through the tube is 4.15 inches of water. As a result, even distribution of the gas-air mixture is obtained and ya combustion zone surrounds the permeable tube over the entire thickness of the deposit. This example is by way of illustration only and is not to be construed as limiting the scope of the invention which is directed to providing an elongated combustion zone throughout the entire depth of thick mineral deposits.

I claim:

1. A burner in combination with a well bore which penetrates an oil sand interval to be heated, a combustible gas and an air supply conduit connected to the upper end of a tubing string, said tubing string extending into said well bore and connected therein to said burner, a casing within the upper extremity of said well bore and -a conduit communicating with said oasing for the removal of ue gases therefrom; said burner comprising an elongated metal tube perforated along its length and connected to said tubing string, a second perforated metal tube concentric with and surrounding said first tube, said second tube being7 of lesser diameter than said well bore to form an annulus therebetween, a first ring laterally positioned between the non-perforated ends of said first and second tubes, and a second ring laterally positioned between the opposite non-perforated ends of said tubes, a cap over the lower end of said first tube, a first metal screen around the outer periphery of said first tube extending from said first ring to said second ring, a second metal screen around the inner periphery of said second tube extending from said first ring to said second ring, and an annular bed of unconsolidated granular material packed between said first and second screens and said first and second rings.

2. The combination of claim 1 wherein said well bore penetrates a plurality of oil sand inten/als to be heated and wherein a plurality of said burners are attached to said tubing string so as to extend substantially the depth of its respective oil sand interval. i

3. The combina/tion of a Well bore penetrating a subterranean oil sand interval which comprises a first tubing string and a second tubing string concentrically disposed within said first tubing string, said first and second tubing strings extending into said well bore, a conduit communieating with the upper end of said well bore for removal of iue gas therefrom, said second tubing string extending to the upper level of said oil sand interval, said first tubing string extending to the lower level of said oil sand interval, a gas permeable tube concentrically disposed within said first tubing string and connected to the lower end of said second tubing string, said gas permeable tube being closed at its lower end and terminating at the lower level of said oil sand interval, said gas permeable tube having an uninterrupted wall of uniform permeability to gases so as to permit diffusion of a gas therethrough, a combustible gas supply conduit connected to the upper end of said second tubing string, an oxidizing gas supply conduit connected to the upper end of said first tubing string, a combustible gas supply means connected to said combustible gas supply conduit and an oxidizing gas supply means connected to said oxidizing supply conduit, said combustible gas supply means being adapted to supply combustible gas lat a pressure greater than the pressure of oxidizing gas supplied by said oxidizing gas supply means so as to cause said combustible gas to diffuse through said gas permeable tube and admix with said oxidizing gas within said first tubing string.

References Cited in the file ot' this patent UNITED STATES PATENTS 71,144 Dean Nov. 19, 1867 444,85() Reed Jan. 20, 1891 1,678,592 Garner et ral. July 24, 1928 2,161,865 Hobstetter et al. June 13, 1939 2,890,754 Hoifstrom et al June 16, 1959 2,913,050 lCrawford Nov. 17, 1959 2,981,332 Miller et al Apr. 25, 1961 3,010,516 Schleicher Nov. 28, 1961 3,050,116 Crawford Aug. 21, 1962 FOREIGN PATENTS 123,137 Sweden Nov. 9, 1948 

3. THE COMBINATION OF A WELL BORE PENETRATING A SUBTERRANEAN OIL SAND INTERVAL WHICH COMPRISES A FIRST TUBING STRING AND A SECOND TUBING STRING CONCENTRICALLY DISPOSED WITHIN SAID FIRST TUBING STRING, SAID FIRST AND SECOND TUBING STRINGS EXTENDING INTO SAID WELL BORE, A CONDUIT COMMUNICATING WITH THE UPPER END OF SAID WELL BORE FOR REMOVAL OF FLUE GAS THEREFROM, SAID SECOND TUBING STRING EXTENDING TO THE UPPER LEVEL OF SAID OIL SAND INTERVAL, SAID FIRST TUBING STRING EXTENDING TO THE LOWER LEVEL OF SAID OIL SAND INTERVAL, A GAS PERMEABLE TUBE CONCENTRICALLY DISPOSED WITHIN SAID FIRST TUBING STRING AND CONNECTED TO THE LOWER END OF SAID SECOND TUBING STRING, SAID GAS PERMEABLE TUBE BEING CLOSED AT ITS LOWER END AND TERMINATING AT THE LOWER LEVEL OF SAID OIL SAND INTERVAL, SAID GAS PERMEABLE TUBE HAVING AN UNINTERRUPTED WALL OF UNIFORM PERMEABILITY TO GASES SO AS TO PERMIT DIFFUSION OF A GAS THERETHROUGH, A COMBUSTIBLE GAS SUPPLY CONDUIT CONNECTED TO THE UPPER END OF SAID SECOND TUBING STRING, AN OXIDIZING GAS SUPPLY CONDUIT CONNECTED TO THE UPPER END OF SAID FIRST TUBING STRING, A COMBUSTIBLE GAS SUPPLY MEANS CONNECTED TO SAID COMBUSTIBLE GAS SUPPLY CONDUIT AND AN OXIDIZING GAS SUPPLY MEANS CONNECTED TO SAID OXIDIZING SUPPLY CONDUIT, SAID COMBUSTIBLE GAS SUPPLY MEANS BEING ADAPTED TO SUPPLY COMBUSTIBLE GAS AT A PRESSURE GREATER THAN THE PRESSURE OF OXIDIZING GAS SUPPLIED BY SAID OXIDIZING GAS SUPPLY MEANS SO AS TO CAUSE SAID COMBUSTIBLE GAS TO DIFFUSE THROUGH SAID GAS PERMEABLE TUBE AND ADMIX WITH SAID OXIDIZING GAS WITHIN SAID FIRST TUBING STRING. 